Compact low noise efficient blower for CPAP devices

ABSTRACT

A blower includes an electric motor having a shaft, a housing having an inlet and outlet between which is defined a gas flow path, the outlet structured to direct gas exiting the blower in an axial first direction, a first impeller attached to the shaft and adapted to accelerate air tangentially and direct it radially outward, a stationary portion, and a shield. The stationary portion includes a first stator vane structure defining a plurality of stator vane leading edges and a stator vane outer radial edge. The first stator vane structure is arranged to direct gas flow along a curved path that directs flow at an inner end thereof in a radially inward direction. The shield has an outer edge extending radially beyond the outer radial edge of the first stator vane structure and is adapted to isolate the stator vane leading edges from an impeller blade pressure pulse.

CROSS-REFERENCE TO APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/926,657, filed Dec. 2, 2012, allowed, which is a continuation of U.S.patent application Ser. No. 12/227,637, filed Nov. 24, 2008, now U.S.Pat. No. 7,866,944, which is the U.S. national phase of InternationalApplication No. PCT/AU2007/000719, filed May 24, 2007, which designatedthe U.S. and claims the benefit of Australian Provisional ApplicationNo. AU 2006902781, filed May 24, 2006, each of which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to an efficient, low-noise, compact blower. Theblower may be used in a range of devices including medical, cleaning,automotive or computer devices. The blower may also be used as anextractor or suction device. In an embodiment, the blower may be used ina non-invasive ventilation (NIVV) device such as a CPAP or ventilatordevice.

BACKGROUND OF THE INVENTION

Nasal CPAP Treatment of OSA

Nasal Continuous Positive Airway Pressure (CPAP) treatment ofObstructive Sleep Apnea (OSA) was invented by Sullivan. See U.S. Pat.No. 4,944,310. Apparatus for treating OSA typically comprises a blowerthat provides a supply of air or breathable gas to a patient interface,such as a mask, via an air delivery conduit. Since patients typicallysleep while wearing the device, it is desirable to have a system whichis quiet and comfortable.

Generic Blower/Air Pump

Blowers are typically classified as centrifugal, axial or mixed flow.Generally, blowers comprise two main parts: a rotating part, namely animpeller and shaft; and a stationary part that defines a fluid flowpath, typically a chamber such as a volute. Rotation of the impellerimparts kinetic energy to the air. The stationary part redirects the airexpelled from the impeller into an enclosed outlet passage. During thisredirection, resistance is encountered to flow because of the pressuregenerated by downstream resistance or a downstream pressure source. Asthe flow is slowed against this resistance, a portion of the kineticenergy is converted to potential energy in the form of pressure.

Generally, the faster the impeller is rotated, the higher the pressurethat will be developed. A less effective blower must rotate its impellerfaster to generate the same pressure as a more effective blower.Generally, running a given blower slower makes it quieter and prolongsits life. Hence, it is generally desirable to make blowers moreeffective at generating a supply of air at positive pressure.

With reference to FIGS. 1 and 2, three directions are defined, i.e.,radial R, tangential T and axial A. Prior art centrifugal blower 10includes an outlet 20, an inlet 30, an electric motor 40, an impeller 50and a shaft 60. Arrows 70 indicate the general direction of airflow. Airenters the blower at the inlet 30 and is accelerated by the rotatingimpeller. The rotation imparted by the impeller generally directs theairflow in a tangential direction T. The volute then constrains theairflow to spiral the volute. The airflow then exits the blower in agenerally tangential direction T via the outlet 20.

In some blowers, such as axially developed volute blowers, the volutegeometry directs the tangential spiraling airflow in a slight axialdirection A prior to exiting the blower in a generally tangentialdirection T.

The performance of a blower is often described using fan curves, whichshow the flow rate of air versus outlet pressure of air. Many factorsaffect the fan curve including impeller diameter and the number andshape of the impeller blades. The design process is a complex balancebetween competing priorities such as desired pressure, flow rate, size,reliability, manufacturability and noise. While many combinations ofsize, shape and configuration of components may produce a flow ofpressurized air, such a result may be far from optimal, or beimpractical.

ResMed Axial Volute Design

Another form of known blower design is described in ResMed'sInternational Patent Application PCT/AU99/00444, published as WO99/64747, the contents of which are hereby expressly incorporated byreference. As described in this patent application, the volute geometrydevelops in a generally axial direction, however air exits this blowerin a generally tangential direction.

Respironics Ventilator

Respironics International Patent Application PCT US98/19635, publishedas WO 99/13932, describes a medical ventilator which has a blowerassembly that preferably includes three rotating impellers and twostationary stators. In this device, a conventional volute design is usedsuch that air exits the blower assembly in a generally tangentialdirection.

A disadvantage of this blower design is it tends to suffer from bladepass tonal noise emission.

Respironics REMstar

Another known blower is found in the Respironics REMstar series of CPAPdevices. In this device, air exits the blower in a generally tangentialdirection.

ResMed Blowers

U.S. Pat. No. 6,910,483 (Daly et al) assigned to ResMed Limiteddescribes a double ended variable speed blower for Continuous PositiveAirway Pressure (CPAP) ventilation of patients that includes twoimpellers in the gas flow path that cooperatively pressurize gas todesired pressure and flow characteristics. The contents of this patentare hereby expressly incorporated by reference. In this device, airexits the blower in a generally tangential direction.

PCT Application Nos. PCT/AU2006/001617, filed Oct. 27, 2006, andPCT/AU2006/001616, filed Oct. 27, 2006, describe multiple stage blowers.The contents of both of these PCT applications are hereby incorporatedby reference.

As noted above, known CPAP and VPAP blowers use a more or lessconventional volute design, namely one where the air leaves the volutetangentially. These designs have the disadvantage that the asymmetry ofthe volute leads to asymmetry of flow patterns in the volute andimpeller. This problem is especially significant at flow rates away fromthe ideal “design” flow rates of the volute. CPAPs and VPAPs,unfortunately, are used for a substantial portion of their operationaltime under non-ideal flow conditions as a consequence of very highexcursions in the flow demand. This means that the flow patterns withinthe volute, and consequently within the impeller, become highlyasymmetrical, uneven, and even unstable. This in turn leads to pressurepulses and turbulence. As a consequence, acoustic blade pass tonal noiseand turbulence noise are produced.

SUMMARY OF THE INVENTION

A first aspect of the invention is directed to a respiratory device thatquietly and effectively provides a supply of air at positive pressure.Another aspect of the invention is to provide a blower for a NIVV devicefor use in treatment of a range of respiratory diseases. Another aspectof the invention is to achieve a large pressure delivery for a givenmotor speed. Another aspect of the invention is a blower that can supplya given pressure at a relatively low motor speed and with a fastresponse time. Another aspect of the invention is a blower that hasreduced blade pass tonal noise emission and/or turbulence noiseemission.

In one form of the invention suitable for respiratory devices, theblower is configured to provide air pressurized in the range of 2 cm H₂Oto 100 cm H₂O. In another form suitable for treatment of SleepDisordered Breathing, the blower is configured to provide pressure inthe range of 2 cm H₂O to 30 cm H₂O.

In one form, the blower is configured to provide air at flow rates up to200 L/min. In one form, the blower is configured to provide air at flowrates ranging −50 L/min to +200 L/min.

In one form of the invention suitable for respiratory devices, theblower comprises at least one impeller having a relatively smalldiameter, for example in the range of 20 to 200 mm. In an embodiment,the impeller comprises two differently sized shrouds to provide a rigidimpeller with relatively low inertia. The impeller may be injectionmolded from plastic such as polycarbonate or polypropylene.

An aspect of the invention is that the stationary portion of the blowerdefines an airflow path that is quiet and efficient. In an embodiment,the stationary portion defines an airflow path that is substantiallyaxially symmetrical.

An aspect of the present invention has a stationary portion or volutedesign that is substantially axially symmetric on all stages. So nomatter what the flow rate, the air feed pattern through the impellerblade passages, and in the volute, remains symmetrical and steady. Thisleads to lower strength pressure pulses and less turbulence, which inturn lead to lower levels of acoustic blade pass tone, and lower levelsof turbulence noise.

In one form, the blower has one stage. In other forms of the invention,the blower has more than one stage. In forms of the invention wheremultiple stages are used along an axis, the motor may be positioned inthe center and similar numbers of impellers may be positioned on eitherside of the motor along the axis.

In an embodiment, the stationary component of the blower includes a vanestructure that receives airflow from an impeller and directs it in aradial direction. In an embodiment, the blower includes a shieldpositioned between an impeller and a vane structure to direct airflow tothe stator inlet vanes in an orientation favorable to minimize lossesand turbulence. In an embodiment, the airflow is directed in an axialdirection between the impeller and vane structure. In an embodiment, theshield also presents a barrier between the impeller blades and thestator vane leading edges such that impeller blade pressure pulses aresubstantially isolated from the stator vanes.

Another aspect of the invention relates to a blower for supplying air atpositive pressure including a stationary portion including an inlet andan outlet, a rotating portion provided to the stationary portion, and amotor adapted to drive the rotating portion. The inlet and outlet areco-axially aligned along an axis of the stationary portion such that airenters and exits the stationary portion in a generally axial direction.

Another aspect of the invention relates to a method for supplying air atpositive pressure to a patient for treatment including providing air toa blower via an inlet that is axially aligned with an axis of theblower, directing the air through one or more stages of the blower, andsupplying the air at positive pressure via an outlet that is axiallyaligned with the inlet.

Another aspect of the invention relates to a blower for supplying air atpositive pressure including a stationary portion including an inlet andan outlet, a rotating portion provided to the stationary portion, and amotor adapted to drive the rotating portion. The stationary portionincludes a shield to isolate stator vanes of the stationary portion fromimpeller blades of the rotating portion. The shield includes a tubeportion having an interior surface and an exterior surface. The interiorsurface is adapted to support a bearing of the rotating portion and theexterior surface is adapted to support a stator assembly of the motor.

Other aspects, features, and advantages of this invention will becomeapparent from the following detailed description when taken inconjunction with the accompanying drawings, which are a part of thisdisclosure and which illustrate, by way of example, principles of thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings facilitate an understanding of the variousembodiments of this invention. In such drawings:

FIG. 1 shows a plan view of a generic prior art blower assembly;

FIG. 2 shows an elevation view of the generic prior art blower assemblyshown in FIG. 1;

FIGS. 3 a to 3 g show various views of a blower according to anembodiment of the invention;

FIGS. 4 a to 4 c show various exploded views of the blower shown inFIGS. 3 a-3 g;

FIGS. 5 a to 5 g show various views of the blower shown in FIGS. 3 a-3g;

FIGS. 6 a to 6 g show various views of an impeller according to anembodiment of the invention;

FIGS. 7 a to 7 d show various views of a stator component according toan embodiment of the invention;

FIGS. 8 a to 8 c show various views of a shield according to anembodiment of the invention;

FIG. 9 shows a two-shrouded impeller according to an alternativeembodiment of the invention;

FIGS. 10 a to 10 b show various views of an alternative stator componentaccording to an alternative embodiment of the invention;

FIGS. 11-14 show various views of a blower according to anotherembodiment of the present invention;

FIG. 15 is an exploded view of the blower shown in FIGS. 11-14;

FIG. 16 is a cross-section view of the blower shown in FIGS. 11-14;

FIG. 17 is a cross-sectional view illustrating a support system for ablower according to an embodiment of the present invention;

FIG. 18 is a cross-sectional view of a blower according to anotherembodiment of the present invention; and

FIG. 19 is a cross-sectional view of a blower according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Aspects of the invention will be described herein in its application tonon-invasive ventilation (NIVV) treatment apparatus (e.g., positiveairway pressure (PAP) devices or flow generators), such as CPAP,mechanical ventilation and assisted respiration, but it is to beunderstood that the features of the invention will have application toother fields of application where blowers are used, such as vacuumcleaners, cooling equipment in computers and HVAC devices such as thosefound in buildings and vehicles.

In this specification, the words “air pump” and “blower” may be usedinterchangeably. In this specification, the phrase “stationary part”will be taken to include “volute”. The term “air” will be taken toinclude breathable gases, for example air with supplemental oxygen. Itis also acknowledged that the blowers described herein may be designedto pump fluids other than air.

In this specification, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise”, “comprised” and “comprises” where they appear.

While particular embodiments of this invention have been described, itwill be evident to those skilled in the art that the present inventionmay be embodied in other specific forms without departing from theessential characteristics thereof. The present embodiments and examplesare therefore to be considered in all respects as illustrative and notrestrictive, the scope of the invention being indicated by the appendedclaims rather than the foregoing examples or description, and allchanges which come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein. It will further beunderstood that any reference herein to known prior art does not, unlessthe contrary indication appears, constitute an admission that such priorart is commonly known by those skilled in the art to which aspects ofthe invention relate.

1. General Description

A blower 100 according to an embodiment of the invention may be in theform of a centrifugal air pump comprising a stationary portion, arotating portion and an electric motor.

In an exemplary embodiment as shown in FIGS. 3 a-5 g, the stationaryportion includes an external housing 170 in two parts 172, 174 and anassembly of internal flow directing components including three sets ofstator components 180, 182, 184 and two shields 190, 192. The rotatingportion comprises three impellers 150, 152, 154 and a shaft 160 adaptedto be driven by electric motor 140. In an embodiment, the electric motor140 may be a brushless D.C. motor. In the illustrated embodiment, theblower has three stages each with a corresponding impeller and set ofstationary vanes and shields. As shown in FIGS. 3 a-3 g and 4 a, theblower 100 is generally cylindrical and has an inlet 130 at one end andan outlet 120 at the other end.

In the illustrated embodiment, all the components of the blower arealigned along the shaft of the motor which defines an axis about whichall components are generally symmetric. In an embodiment, the blower maybe self similar sector-wise about its axis. This axial symmetry mayapply to all stages.

An advantage of the blower according to an embodiment of the presentinvention is that it promotes symmetrical and stable flow patternswithin the volute over the range of pressures and flow rates encounteredduring use. Thus, blade pass tone and turbulence noise emissions arereduced.

An advantage of the illustrated embodiment is the ease of manufactureand of assembly offered by the component geometry, particularly ifinjection molded, and by the stacked nature of the assembly.

2. Fluid Flow Path

2.1 First Stage

The first stage of the blower will now be described. As best shown inFIGS. 4 a-4 c and 5 a-5 g, air enters the blower 100 at the inlet 130and passes into the first rotating impeller 150 where it is acceleratedtangentially and directed radially outward. It then passes around thesides of the motor 140 flowing in a spiral manner with a largetangential velocity component and also an axial component towards thefirst set of stator vanes 185 in stator component 180. In thisembodiment, no shield is provided for the first stage since theshielding function is provided by the motor case. At the first set ofstator vanes 185, air is directed radially inwardly towards orifice 181,and thereafter onto the second stage.

2.2 Second Stage

In the second stage, as shown in FIGS. 4 a-4 c and 5 a-5 g, air is firstaccelerated tangentially by second rotating impeller 152 and also flowsoutwardly in a radial direction. Air then flows in a spiral manner witha large tangential velocity component and also an axial componentpassing through the gap 164 defined by the outer edge of circular disc190 and the inner surface of the stator component 182. Air then entersthe second set of stator vanes 187 formed in stator component 182 and isdirected radially inwardly towards orifice 183, and thereafter onto thethird stage.

2.3 Third Stage

The fluid flow path in the third stage is similar to the fluid flow pathin the second stage. As shown in FIGS. 4 a-4 c and 5 a-5 g, air entersthe stage via orifice 183 and is accelerated tangentially and alsodirected outwardly in a radial direction by third rotating impeller 154.Air then flows in a spiral manner with a large tangential component andalso an axial component passing through the gap 166 defined by the outeredge of circular disc 192 and the inner edge of the housing 174. The airthen is directed by stator vanes 184 formed in the housing 174 towardsthe outlet 120.

3. Stationary Portion

3.1 General

The stationary portion of the blower includes the two external housingparts 172, 174, the internal flow directing stator components 180, 182,184 and two shields 190, 192 and may be made from any suitable rigid orsemi-rigid material that is dimensionally stable. In an embodiment, thestator component may be made from material that provides one or more ofthe following characteristics: good thermal conductivity; relatively lowcost; low density; acoustic dampening properties; and ease of molding toreduce post machining. The use of thermally conductive material may alsoassist in keeping the motor cool and warming the air. The ability toheat the air may provide an additional advantage for blowers used inNIVV devices.

In an embodiment, at least some of the components of the stationaryportion may be made from aluminum, or an alloy thereof, e.g., aluminumdie castings. In another embodiment, at least some of the components ofthe stationary portion may be made from magnesium, or an alloy thereof.In yet another embodiment, at least some of the components of thestationary portion may be made from a plastic material.

3.2 Inlet

The air inlet 130 is adapted to allow sufficient airflow into the blowerto ensure desired flow requirements are met while not allowing excessivenoise emission back out of the air inlet 130. Also, the dimensions ofthe air inlet 130 are dependent upon the desired level of flow requiredby the blower and the particular application of use. In a NIVVembodiment, the air inlet 130 may have a diameter between 2 mm and 100mm, e.g., between 15 mm and 20 mm.

3.3 Stator Components

The stator components including stator vanes are structured to promote asmooth transition in flow direction. In an embodiment, two of the statorcomponents 180, 182 are injection molded from a plastic (e.g., see FIGS.7 a-7 d). The third stator component includes stator vanes 184 moldedinto the bottom casing 174. In another embodiment, the stator vanes maybe made using a thermally conductive material such as metal.

3.3.1 Radial Flow Direction

In an NIVV embodiment of the invention, the stator vanes direct flow ina generally radial direction. The vanes have a height in the range of 1mm to 100 mm, e.g., 3 mm to 5 mm. This arrangement brings the flowthrough an approximate right angle and assists in maintaining a compactdesign for the blower as a whole when compared to vanes orstage-to-stage paths that include a significant axial component.

3.3.2 Shape

Each stage has a plurality of stator vanes to direct the airflow, e.g.,between 2 and 100 stator vanes. In one embodiment, each stage has 7stator vanes. Each vane is substantially identical and has a generallyspiral shape with a radius of curvature that is smaller at its inner endthan at its outer end, to decelerate the air before turning it too hard.

In other applications, such as ones where very high flow rates areneeded and noise is not a main consideration, the air may not bedecelerated by the stator vanes.

3.3.3 Mixed Axial/Radial Flow Direction

In an alternative embodiment of the invention, the vanes may direct flowin a plane normal to the axis, or there may be an axial component to thedirected flow such that at least one set of stator vanes direct flow inboth radial and axial directions. In such an embodiment, the statorvanes on the final stage can be positioned on an incline or otherwiseare not of constant height, but develop axially as well as radially,such that the air is turned more gradually to the axial direction. Forexample, FIGS. 10 a and 10 b illustrate impeller 250 attached to motorshaft 260, a shield 290, and a stator 280 including stator vanes 285structured to direct flow in both radial and axial directions. Thus, thevanes begin tangentially (as they do in the above embodiments), but endup directing the flow axially (rather than radially as in the aboveembodiments). This arrangement may improve pressure generation, thoughit takes up a little more space. This arrangement means that air doesnot pass through a right angle.

3.4 Shield Isolating Stator Vanes

Another aspect of the invention relates to a shield, located betweenstator vanes and impeller blades (e.g., see FIGS. 8 a-8 c). In anembodiment, the shield is formed of injection molded plastic althoughother suitable materials (such as metals) may be used. In theillustrated embodiment, the shield extends radially beyond the outeredge of the stator vanes. This means there is not a “line-of-sight” pathbetween the stator vanes and impeller blades and consequently acts toensure that the airflow impinging on the stator blades is of a uniformcirculating nature.

As best shown in FIGS. 5 b, 5 d, and 5 e, shield 190, 192 directs theflow via an annular aperture 164, 166, respectively. A peripheralaperture may also be used. In one form, the shield leaves only a narrowannular gap between its outer edge and the wall of the stationaryportion. The gap is sufficient to allow enough airflow to the next stagewithout introducing excessive pressure drop. In an embodiment for ablower for use in a NIVV device, the gap may be between 0.5 mm and 100mm, e.g., between 1 mm and 2 mm. The shield also provides an acousticbarrier by isolating the impeller blade pressure pulses from the statorvanes.

In one form, the shield is a circular disc and in NIVV devices may bewelded to the stator vanes.

In an alternative embodiment, the shield may rotate. Such a rotatingshield may be integral to the impeller such that the lower shroud actsas a rotating shield between the impeller blades and stator vanes. Forexample, FIG. 9 illustrates impeller 350 attached to motor shaft 360.The impeller 350 includes upper and lower shrouds 352, 354 with thelower shroud 354 acting as a rotating shroud between impeller blades 355and stator vanes 385 of stator 380.

3.5 Outlet

In contrast to the known prior art centrifugal blowers which direct airexiting the blower in a generally tangential direction, a centrifugalblower in accordance with an embodiment of the present invention directsair in a generally axial direction. This axis-symmetry is effective inreducing airflow turbulence and in reducing blade pass tone, as theimpeller and vanes experience symmetrical flow patterns at all deviceflow rates.

3.6 Housing

The housing comprises chamfers on the external housing to assist withfitting the separate components of housing together. This design allowsfor an overall smaller package.

A gap between the interior wall of the external housing and the externalwall of motor allows air to pass down around the sides of the motor. Inan embodiment, the size of the gap is sufficient to prevent significantfrictional losses but not too large that the overall size of the devicebecomes excessive. In an embodiment for a blower used in NIVV devices,the size of the gap may be between 0.1 mm and 100 mm, e.g.,approximately 4 mm.

The ability of the air to flow around the motor may assist in keepingthe motor cool. It may also assist in heating the patient air in an NIVVdevice.

4. Rotating Portion

4.1 Impeller

In an NIVV embodiment, a blower comprises a plurality of impellers 150,152, 154 as shown in FIGS. 4 a to 4 c. In the illustrated embodiment,the impellers are identical in design, thus only impeller 150 will bedescribed in detail. With particular reference to FIGS. 6 a to 6 g,impeller 150 is of one-piece molded plastic construction, although othersuitable materials and manufacturing techniques could be employed. Theimpeller 150 comprises a plurality of continuously curved blades 200sandwiched between a pair of disk-like shrouds 202, 204. The smallershroud 202 incorporates the hub or bushing 206 that is adapted toreceive the motor shaft 160. The shroud 202 overlaps an inner portion ofthe blades 200, i.e., the outer diameter (OD) of the smaller shroud issubstantially smaller than the OD of the larger shroud 204. The largershroud 204 is formed with a relatively large center opening 208 andextends to the radially outer tips of the blades. Making the OD of thesmaller shroud 202 slightly smaller than the diameter of the centeropening 208 in shroud 204 facilitates the molding process used tomanufacture the impellers.

By utilizing differentially sized shrouds, the inertia of the impeller150 is reduced while the overall rigidity of the impeller is maintained.In this regard, the impeller 150 may be constructed of a polycarbonate,polypropylene, polyamide, or other material which provides acousticdampening properties that dampen the resonance of the impellers. Glassfiber reinforcement may be employed to increase the stiffness of any ofthese materials.

4.1.1 Diameter

In an NIVV embodiment, the impeller 150 may have a diameter in the rangeof 20 mm to 200 mm. In one embodiment, the impeller 150 may have adiameter in the range of 40 mm to 50 mm, for example 42 mm. An impellerwith a diameter in this range may provide a good compromise betweenoverall size of the blower, rotational inertia, and turbulence levels.

4.1.2 Number of Blades

In an NIVV embodiment, the impeller has 4-100 primary blades 200, e.g.,11. The impeller may include secondary and tertiary blades and may be ofvariable blade passage cross section (not shown).

4.1.3 Blade Shape

In an embodiment, the impeller blades 200 are continuously curved inradial direction, and may also be tapered in width in the radially outerportions. The reduced width at the tips of the blades may reduceturbulence (e.g., Reynolds number is less in blowers with 3 impellers, 2impellers, 1 impeller (in order)). In one embodiment, the outermosttransverse edges of the blades may be stepped along their respectivetransverse widths (not shown) to assist in reducing turbulence noise atthe tips of the blades. In another embodiment, the outermost transverseedges of the blades 200 are flat. In an embodiment, the blades 200 havean outlet height in the range of 1 mm to 40 mm, e.g., 3 to 6 mm. In oneform, the blades 200 have an inlet height that is the same as the outletheight, however in other forms, the inlet and outlet heights may bedifferent.

The blades 200 have an inlet angle with respect to a tangent of between0° and 90°, e.g., about 20°. The blades have an outlet angle withrespect to a tangent between 70° and 110°, however other angles arepossible.

4.2 Shaft

In an embodiment, there is a gap between the shaft 160 and the shields190, 192. This gap is sufficient to allow the shaft to rotate within theshields but is small enough to prevent significant leak between theimpellers 152, 154 and the internal flow directing components 182, 184.In a blower for a NIVV device, the gap may be less than 10 mm, e.g.,less than 2 mm.

5. Axial Symmetry

The blower according to an embodiment of the present invention comprisesaxially symmetric volutes, using stator vanes. The airflow enters andexits each stage within the blower in a substantially axial direction.Consequently, the air enters the blower axially at one end, and leavesit axially at the other. The airflow path is substantially axiallysymmetrical throughout the blower maintaining a constant feed patternthrough the impeller, and in the volute. The symmetric blower providesbalance, which leads to lower levels of blade pass tone, and lowerlevels of turbulence noise. Shields positioned between the impeller andthe stator vanes provide a barrier for the vane leading edges from theimpeller blade tips, thus reducing blade pass tone.

6. Multiple Stages

In the illustrated embodiment, the blower includes three stages withthree corresponding impellers. In this embodiment, one impeller ispositioned on one side of the motor and two impellers on the other sideof the motor.

In an alternative embodiment, the blower may include two stages, one oneither side of the motor. Another further embodiment uses four stages,with two on either side of the motor. Another embodiment is a singlestage design. A further embodiment comprises multiple stages only on oneside of the motor.

7. Alternative Embodiments

The following illustrates blowers according to alternative embodimentsof the present invention. In each embodiment, air enters the bloweraxially at one end, and leaves the blower axially at the other end.

7.1 Two-Stage Blower

FIGS. 11-16 illustrate a blower 400 according to another embodiment ofthe present invention. As illustrated, the blower 400 includes twostages with two corresponding impellers 450, 452. In this embodiment,the two impellers are positioned on the same side of the magnet 462 andthe stator assembly 465 but a bearing 444 is positioned between theimpellers 450, 452.

Such blower may be used in Snore PAP, CPAP, APAP, and/or VPAP and may beconfigured to provide a ventilator variant.

7.1.1 Compact Size

The blower 400 has a relatively tiny size to provide a more compact orminiature blower. For example, as shown in FIG. 14, the blower 400 mayhave an overall diameter d of about 50-60 mm, e.g., 53 mm, and anoverall length l of about 40-50 mm, e.g., 44 mm. However, other suitablesizes are possible.

7.1.2 General Description

The stationary portion of the blower 400 includes a housing 470 withfirst and second housing parts 472, 474, a stator component 480including stator vanes 485, and first and second shields 490, 492. Therotating portion of the blower 400 includes first and second impellers450, 452 adapted to be driven by motor 440. The motor includes a magnet462 provided to shaft 460 and a stator assembly 465 to cause spinningmovement of the shaft 460. In an embodiment, the motor may include 2poles (for compact size), be sensorless, and/or be slotless (for lownoise).

The blower 400 is generally cylindrical and has an inlet 430 provided bythe first housing part 472 at one end and an outlet 420 provided by thesecond housing part 474 at the other end. As best shown in FIGS. 12 and16, the outlet 420 has an annulus or ring shape. In an embodiment, theinlet may also have an annulus or ring shape (not shown).

Similar to the above embodiments, the blower 400 has axial symmetry andair enters the blower axially at one end and leaves the blower axiallyat the other end. Such arrangement may provide relatively low noise inuse, e.g., due to axial symmetry and/or low volute turbulence.

7.1.3 Stationary Portion

As best shown in FIGS. 15 and 16, the stator component 480 includes acylindrical hub 486 that engages within a corresponding opening 491provided to the shield 490, e.g., press-fit, to secure the shield 490 inposition. In addition, the hub 486 provides a recess 488 to retain orhouse a bearing 444 that rotatably supports the shaft 460. Asillustrated, the bearing 444 is recessed into the stator component 480so that it is positioned along a plane of where air is fed from theimpeller 450. This arrangement saves space axially because the bearing444 is positioned out of the housing that encloses the motor component,i.e., stator assembly and magnet.

As best shown in FIGS. 15 and 16, the housing part 474 includes statorvanes 487 to direct flow towards the outlet 420. In addition, thehousing part 474 includes an outer annular flange 478 and a hub 475 thatprovides an inner annular flange 476 to support motor components.Specifically, the inner annular flange 476 retains or houses a bearing446 that rotatably supports the shaft 460. The outer annular flange 478retains or housings the stator assembly 465. The shield 492 engages theouter annular flange 478, e.g., press-fit, to enclose the statorassembly 465 along with the magnet 462 on the shaft 460 within thehousing part 474.

In an embodiment, the housing part 474 may be constructed of metal sothat the housing part 474 can act as a heat sink to conduct anddissipate heat generated from the stator assembly 465 in use. Also, atleast a portion of the outer annular flange 478 supporting the statorassembly 465 is exposed to the flow of air, which allows cooling of thestator assembly 465 as air flows through the housing part 474 in use.However, the housing part along with other blower components may beconstructed of other suitable materials, e.g., aluminum, plastic, etc.

7.1.4 Rotating Portion

In the illustrated embodiment, each impeller 450, 452 includes aplurality of continuously curved or straight blades 454 sandwichedbetween a pair of disk-like shrouds 455, 456. The lower shroud 456incorporates the hub or bushing that is adapted to receive the shaft460. Also, each impeller 450, 452 includes a tapered configurationwherein the blades 454 taper towards the outer edge. Further details ofimpellers are disclosed in PCT Application No. PCT/AU2006/001617, filedOct. 27, 2006, which is incorporated herein by reference in itsentirety. Such arrangement may provide relatively fast pressureresponse, e.g., due to relatively low inertia impellers.

7.1.5 Fluid Flow Path

In the first stage, air or gas enters the blower 400 at the inlet 430and passes into the first impeller 450 where it is acceleratedtangentially and directed radially outward. Air then flows in a spiralmanner with a large tangential velocity component and also an axialcomponent passing through the gap 464 defined by the outer edge of theshield 490 and the inner surface of the housing part 472. Air thenenters the stator vanes 485 formed in the stator component 480 and isdirected radially inwardly towards orifice 483, and thereafter onto thesecond stage.

In the second stage, air or gas passes into the second impeller 452where it is accelerated tangentially and directed radially outward. Airthen flows in a spiral manner with a large tangential velocity componentand also an axial component passing through the gap 466 defined by theouter edge of the shield 492 and the inner surface of the housing part474. Air then enters the stator vanes 487 formed in the housing part 474and is directed towards the outlet 420.

7.1.6 Support System

As shown in FIG. 17, the blower 400 may be supported within an outercasing 415 (e.g., forming a portion of a NIVV device such as a PAPdevice) by a support system. The outer casing 415 includes a base 416and a cover 418 provided to the base 416. The support system includes aside support 424, a top support 425, or a bottom support 426 orcombinations thereof to support the blower 400. The support system mayalso be adapted to provide a seal between the inlet and the outlet sidesof the blower 400.

The side support 424 may be in the form of an annular flexible ringadapted to support the blower in a flexible and/or vibration-isolatedmanner within the outer casing 425. In addition, the flexible ring 424divides the inlet of the outer casing 425 from the outlet of the outercasing 425 to avoid the need for a connection tube that directs flowtowards the outlet of the outer casing. Also, the flexible ring 424 mayprovide a seal between the base 416 and the cover 418 of the outercasing 415.

The bottom support 426 includes a biasing member 427, e.g., leaf spring,and a conducting member 428. In use, the bottom support 426 provides aflexible structure to isolate the blower 400 from the outer casing 415,e.g., vibration isolated. In an embodiment, the conducting member 428 iscoupled with the stator assembly 465 to conduct current from an externalsource to the stator assembly 465.

7.2 Two-Stage Blower with Bearing Tube

FIG. 18 illustrates a two-stage blower 500 according to anotherembodiment of the present invention. The two-stage blower 500 is similarto blower 400 described above. In contrast, the second housing part 574and second shield 592 provide a different structure for supporting motorcomponents.

As illustrated, the second housing part 574 includes stator vanes 587 todirect flow towards the outlet 520. In addition, the housing part 574includes a hub 575 that provides an annular flange 576. The annularflange 576 is structured to engage a lower side of the stator assembly565.

The second shield 592 includes a tube portion 595 extending therefrom(e.g., integrally formed in one piece). As illustrated, the statorassembly 565 is provided along an exterior surface of the tube portion595 such that the stator assembly 565 is enclosed and sandwiched betweenthe annular flange 576 of the second housing part 574 and a taperedprojection 593 on the shield 592.

In the illustrated embodiment, the exterior surface of the statorassembly 565 is exposed to the flow of gas passing through the housingpart 574, which allows cooling of the stator assembly 565 in use. Also,heat from the stator assembly may be used to heat the gas for thepatient without the need for a separate heater.

The interior surface of the tube portion 595 retains or houses a bearing546 that rotatably supports the shaft 560. In addition, the tube portion595 encloses the magnet 562 on the shaft 560, which is aligned with thestator assembly 565. In an embodiment, the tube portion 595 may be“magnetically transparent”, which allows the stator assembly 565 to acton the magnet 562 positioned within the tube portion 595 withoutsignificant loss of flux density and/or increased heat, if any. Furtherdetails of a magnetically transparent tube are disclosed in U.S.Provisional Application No. 60/853,778, filed Oct. 24, 2006, which isincorporated herein by reference in its entirety.

A balance ring 598 may be optionally provided to an end portion of theshaft 560 (e.g., opposite the end portion supporting the impellers).

In the illustrated embodiment, the hub 575 protrudes further outwardlyfrom the housing than the hub 475 of the blower 400 described above.This arrangement may add about 1-10 mm, e.g., 5 mm, to the height of theblower 500, e.g., with respect to the blower 400. For example, theblower 500 may have an overall diameter d of about 50-60 mm, e.g., 53mm, and an overall length l of about 40-55 mm, e.g., 49 mm. However,other suitable sizes are possible.

7.3 Three-Stage Blower with Tapered Configuration

FIG. 19 illustrates a three-stage blower 600 according to anotherembodiment of the present invention. Similar to the three-stage blower100 described above, the blower 600 includes three stages with oneimpeller 650 positioned on one side of the motor 640 and two impellers652, 654 positioned on the other side of the motor 640.

In the illustrated embodiment, each impeller 650, 652, 654 of the blower600 has a tapered configuration. In addition, corresponding portions ofthe housing 670 and stator components 680, 682 are tapered to match thetapered configuration of the impellers 650, 652, 654.

In the illustrated embodiment, each impeller 650, 652, 654 includes aplurality of continuously curved or straight blades 653 sandwichedbetween a pair of disk-like shrouds 655, 656. The lower shroud 656incorporates the hub or bushing that is adapted to receive the shaft660. Also, each impeller 650, 652, 654 includes a tapered configurationwherein the blades 653 taper towards the outer edge. Further details ofimpellers are disclosed in PCT Application No. PCT/AU2006/001617, filedOct. 27, 2006, which is incorporated herein by reference in itsentirety.

The upper wall 673 of the housing part 672 is tapered to match thetapered configuration of impeller 650, and the lower wall 657, 659 ofrespective stator components 680, 682 are tapered to match the taperedconfiguration of impellers 652, 654.

Also, in the illustrated embodiment, a central portion 693 of the lowershield 692 is shaped to direct the airflow down towards the outlet 620.The central portion 693 includes a void 696 along the surface facing theimpeller 654, e.g., to maintain a constant section/thickness for theshield 692 and save on material costs.

As illustrated, the bearings 644, 646 that support the shaft 660 areprovided within the housing 642 of the motor 640. In an alternativeembodiment, another bearing, i.e., a third bearing, may be added towardsthe end of the shaft 660 near the lower impeller 654 to add additionalsupport. In another alternative embodiment, rather than adding a thirdbearing, one of the bearings 644 or 646 within the motor housing 642 maybe maintained in its position and the other of the bearings 644 or 646may be moved towards the end of the shaft 660 near the lower impeller654 to add additional support. However, other bearing arrangements arepossible.

In this embodiment, the blower 600 may be supported within an outercasing 615 (e.g., forming a portion of a NIVV device such as a PAPdevice) by a support system. The support system includes side supports624 to support the sides of the blower 600 and a bottom support 626 tosupport the bottom of the blower 600.

The side and bottom supports 624, 626 may be flexible members, e.g.,elastomer, to isolate the blower 600 from the outer casing 615, e.g.,vibration isolated. As illustrated, the side supports 624 are adapted toengage respective pegs 635 provided to the blower 600. The bottomsupport 626 provides a conduit from the outlet 620 of the blower 600 tothe outlet 617 of the outer casing 615 (e.g., which may connectable toan air delivery conduit to deliver pressurized air to a patient fortherapy).

8. Other Comments

While the invention has generally been described in terms of acentrifugal pump, it is not limited to this form, and may also take theform of a mixed flow type.

An aspect of the invention is that the chamber that defines the airflowpath is generally axially symmetric. This does not mean that the entireairflow path of the device that uses a blower in accordance with theinvention must also be axially symmetric. Variations within the scope ofthe present invention may include some asymmetries. These asymmetriesmay lie in a region where velocities are low such that losses and noiseare less affected.

In an embodiment, the blower allows the airflow feed pattern through theimpeller, and in the volute, to remain symmetrical irrespective of theflow rates. This results in lower levels of blade pass tonal noiseemission, and lower levels of turbulence noise emission.

While the invention has been described in connection with what arepresently considered to be the most practical and preferred embodiments,it is to be understood that the invention is not to be limited to thedisclosed embodiments, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the invention. Also, the various embodiments described abovemay be implemented in conjunction with other embodiments, e.g., aspectsof one embodiment may be combined with aspects of another embodiment torealize yet other embodiments. Further, each independent feature orcomponent of any given assembly may constitute an additional embodiment.In addition, while the invention has particular application to patientswho suffer from OSA, it is to be appreciated that patients who sufferfrom other illnesses (e.g., congestive heart failure, diabetes, morbidobesity, stroke, barriatric surgery, etc.) can derive benefit from theabove teachings. Moreover, the above teachings have applicability withpatients and non-patients alike in non-medical applications.

What is claimed is:
 1. A blower comprising: an electric motor having ashaft that defines a shaft axis; a housing having a housing inlet and ahousing outlet between which is defined a flow path for gas; the housingoutlet is structured to direct gas exiting the blower in an axial firstdirection; a first impeller attached to the shaft and adapted toaccelerate air tangentially and to direct it radially outward; astationary portion including a first stator vane structure including aplurality of stator vanes each having a generally spiral shape, thefirst stator vane structure defining a plurality of stator vane leadingedges, the first stator vane structure further defining a stator vaneouter radial edge, the first stator vane structure having an inner end,the first stator vane structure and its generally spiral-shaped statorvanes thereof being arranged to smoothly direct the gas flow along acurved path, said curved path directing flow at the inner end of thefirst stator vane structure in a radially inward direction; a shieldhaving an outer edge extending radially beyond the outer radial edge ofthe first stator vane structure; said shield adapted to isolate thestator vane leading edges from an impeller blade pressure pulse, whereinthere is an annular gap between he outer edge of the shield and thestationary portion.
 2. A blower according to claim 1, wherein the firstimpeller comprises a plurality of impeller blades sandwiched between afirst disk-like shroud and a second disk like shroud, wherein the outerdiameter of the first shroud is smaller compared to the outer diameterof the second shroud and the shield is constructed and arranged suchthat there is not a line-of-sight path between the first stator vanestructure and the impeller blades.
 3. A blower according to claim 2,wherein the impeller blades have a continuously curved shape.
 4. Ablower according to claim 2, wherein the plurality of impeller bladesare tapered in width in the radially outer portions.
 5. A bloweraccording to claim 2, wherein the plurality of impeller blades have aninlet angle with respect to a tangent of between 0 degrees and 90degrees.
 6. A blower according to claim 2, wherein the plurality ofimpeller blades have an outlet angle with respect to a tangent ofbetween 70 degrees and 110 degrees.
 7. A blower according to claim 2,wherein the first shroud overlaps an inner portion of the blades of theimpeller and includes a hub that is adapted to receive the shaft of themotor.
 8. A blower according to claim 2, wherein the second shroudincludes a center opening and extends to the radially outer tips of theblades of the impeller.
 9. A blower according to claim 1, wherein theshield is a circular disc.
 10. A blower according to claim 1, whereinthe shield is integral to the first stator vane structure.
 11. A bloweraccording to claim 1, further comprising a second impeller displacedaxially from said first stator vane structure, the second impellerincluding a plurality of impeller blades.
 12. A blower according toclaim 11, wherein the first impeller and/or the second impeller are ofone-piece moulded plastic construction.
 13. A device for non-invasiveventilation of a patient comprising: a blower according to claim 1; anouter casing surrounding the blower; and a blower support systemproviding vibration isolation of the blower from the outer casing.
 14. Ablower comprising: an electric motor having a shaft that defines a shaftaxis; a housing having a housing inlet and a housing outlet betweenwhich is defined a flow path for gas; the housing outlet is structuredto direct gas exiting the blower in an axial first direction; a firstimpeller attached to the shaft and adapted to accelerate airtangentially and to direct it radially outward; a stationary portionincluding a first stator vane structure defining a plurality of statorvane leading edges, the first stator vane structure further defining astator vane outer radial edge, the first stator vane structure having aninner end, the first stator vane structure being arranged to smoothlydirect the gas flow along a curved path, said curved path directing flowat the inner end of the first stator vane structure in a radially inwarddirection; a shield having an outer edge extending radially beyond theouter radial edge of the first stator vane structure; said shieldadapted to isolate the stator vane leading edges from an impeller bladepressure pulse, wherein there is an annular gap between the outer edgeof the shield and the stationary portion.
 15. A blower according toclaim 14, wherein the first impeller comprises a plurality of impellerblades sandwiched between a first disk-like shroud and a second disklike shroud, wherein the outer diameter of the first shroud is smallercompared to the outer diameter of the second shroud and the shield isconstructed and arranged such that there is not a line-of-sight pathbetween the first stator vane structure and the impeller blades.
 16. Ablower according to claim 14, further comprising a second impellerdisplaced axially from said first stator vane structure, the secondimpeller including a plurality of impeller blades.
 17. A blowercomprising: an electric motor having a shaft that defines a shaft axis;a housing having a housing inlet and a housing outlet between which isdefined a flow path for gas; the housing outlet is structured to directgas exiting the blower in an axial first direction; a first impellerattached to the shaft and adapted to accelerate air tangentially and todirect it radially outward; a stationary portion including a firststator vane structure defining a plurality of stator vane leading edges,the first stator vane structure further defining a stator vane outerradial edge, the first stator vane structure having an inner end, thefirst stator vane structure being arranged to smoothly direct the gasflow along a curved path, said curved path directing flow at the innerend of the first stator vane structure in a radially inward direction; ashield having an outer edge extending radially beyond the outer radialedge of the first stator vane structure; said shield adapted to isolatethe stator vane leading edges from an impeller blade pressure pulse; anda second impeller displaced axially from said first stator vanestructure, the second impeller including a plurality of impeller blades,wherein the second impeller is associated with a second stator vanestructure that is displaced axially from the second impeller.
 18. Ablower according to claim 17, wherein the first impeller comprises aplurality of impeller blades sandwiched between a first disk-like shroudand a second disk like shroud, wherein the outer diameter of the firstshroud is smaller compared to the outer diameter of the second shroudand the shield is constructed and arranged such that there is not aline-of-sight path between the first stator vane structure and theimpeller blades.
 19. A blower comprising: an electric motor having ashaft that defines a shaft axis; a housing having a housing inlet and ahousing outlet between which is defined a flow path for gas; the housingoutlet is structured to direct gas exiting the blower in an axial firstdirection; a first impeller attached to the shaft and adapted toaccelerate air tangentially and to direct it radially outward; astationary portion including a first stator vane structure defining aplurality of stator vane leading edges, the first stator vane structurefurther defining a stator vane outer radial edge, the first stator vanestructure having an inner end, the first stator vane structure beingarranged to smoothly direct the gas flow along a curved path, saidcurved path directing flow at the inner end of the first stator vanestructure in a radially inward direction; a shield having an outer edgeextending radially beyond the outer radial edge of the first stator vanestructure; said shield adapted to isolate the stator vane leading edgesfrom an impeller blade pressure pulse; and a second impeller displacedaxially from said first stator vane structure, the second impellerincluding a plurality of impeller blades, wherein the first impeller andsecond impeller are attached to opposing ends of the motor shaft.
 20. Ablower according to claim 19, wherein the first impeller comprises aplurality of impeller blades sandwiched between a first disk-like shroudand a second disk like shroud, wherein the outer diameter of the firstshroud is smaller compared to the outer diameter of the second shroudand the shield is constructed and arranged such that there is not aline-of-sight path between the first stator vane structure and theimpeller blades.